Anxiety disorders, the most common mental health problems in children and adolescents, often go untreated while children suffer, even though there are effective treatments available, according to a new report on anxiety in children and adolescents from the Child Mind Institute in New York. Anxiety may be missed because it doesn’t necessarily declare itself with attention-getting disruptive behaviors; in fact, symptoms may keep some children quiet and inhibited, though in other children, alternatively, anxiety may be misunderstood as oppositional behavior.

Adults may also assume that anxiety in a child is just a phase to be outgrown. A certain amount of anxiety is a normal aspect of development for young children — consider separation anxiety, for example — and it can even be protective, since children need to learn to keep themselves safe and anticipate certain kinds of dangers. But when worrying or avoiding possible threats gets in the way of a child’s functioning or a child’s enjoyment, it should be a signal to parents that help is needed, not just watching and waiting, not arranging the child’s life to avoid the occasions of anxiety.

Kathleen Merikangas, the senior investigator and chief of the Genetic Epidemiology Research Branch at the National Institute of Mental Health, said, “To me, anxiety is one of the most underrecognized or under-treated conditions of childhood and adolescence.” These children can get missed, she said, because they may seem to be functioning well; many don’t have the kinds of developmental problems or attention issues that draw attention in school, though they may be suffering.

Consider the child whose anxiety about speaking in public gets in the way of participating in class. The child may be silent out of a fear of being laughed at or otherwise rejected, Dr. Merikangas said, but to the teacher, it may look like the child is just not interested. Environmental modifications can really help these children thrive in school, she said; for example, working in small groups with children they know.

The new report, released in September, summarizes the evidence that early temperament in children predicts their later behavior patterns around anxiety; toddlers who show what are called “behaviorally inhibited” behaviors, which parents are likely to perceive as extreme shyness, or anxiety around new people, are more likely to develop social anxiety later on. That doesn’t mean that shyness is pathological (as with all varieties of temperament, there’s a wide range of function), but it does suggest how important it is to help a child with this temperament who develops difficulties.

But with rates of suicide and suicidal ideation on the rise, it’s particularly important to provide information to schools and to parents about recognizing anxiety and getting children help.

Dr. Harold Koplewicz, the president of the Child Mind Institute, said that when anxiety disorders in children are left untreated, anxiety can inhibit their lives, making standard daily activities difficult, from attending school to sleeping in their own beds, and lead to many extra visits to the school nurse or the pediatrician.

But beyond that, he said, “people underestimate that this is a gateway disorder.” If children don’t get help with these disorders, they may be at risk to develop other mental health problems; the child with severe separation anxiety may develop panic disorder, he said; the child with untreated general anxiety may be at greater risk for depression.

Dr. Merikangas was a co-investigator on a national study of mental disorders in adolescents, which has shown both that anxiety disorders were the most common mental health problems in adolescents in the United States, and also the problems that showed up earliest in those children’s lives — the mean age of onset for anxiety disorders was 6. But many adolescents had never received treatment. That makes it essential to get the word out, Dr. Merikangas said, that anxiety is “one of the most treatable symptoms and syndromes, we can really change their lives with minimal intervention.”

“All these disorders are remarkably treatable,” Dr. Koplewicz said. There are highly effective behavioral and psychosocial therapies, including cognitive behavioral therapies, to help children cope with the demands of daily life. For children who don’t respond to psychosocial therapies, he said, medications can be added.

But perhaps because anxiety is a normal response, parents often believe that even severe and disabling anxiety symptoms are just a phase, and on average, there is a two-year lag between the time children develop anxiety and the time they get help. “It’s bad for these children’s brains,” he said. “Having your brain’s thermostat miss-set is not good for your brain.”

“Anxiety can manifest itself along a continuum,” said Rachel Busman, the senior director of the anxiety disorders center at the Child Mind Institute. The report shows that there is some overlap with physical illnesses, such as chronic headaches or stomach aches, often coordinated with school. “That could be a kid’s way of saying, ‘I’m anxious,’” she said.

And when a child who is having a lot of difficulty with separation gets into the classroom, Dr. Busman said, that child may start throwing things, or running and hiding, and that “bad behavior” may represent the fight or flight response of anxiety. “We’ve also seen kids who have intense social anxiety and their way of managing it is to be class clown,” she said.

Treating children with anxiety always means working with their parents. Jerry Bubrick, senior clinical psychologist at the anxiety disorders center of the Child Mind Institute, said that when children are little, it’s normal for parents to operate in “fix-it mode,” blocking the staircase so a toddler doesn’t tumble down, averting problems before they happen.

As children get older, parents normally pull back, helping children find solutions of their own. “But anxious parents of anxious children remain in fix-it mode,” he said, helping their children avoid the situations that make them anxious. Therapy involves exposing children to those situations and helping them develop strategies to manage them; with treatment, Dr. Bubrick said, parents can “let the child experience the anxiety and learn to tolerate and overcome it on their own.”

“If you see things you’re not sure about, talk to the preschool, talk to the pediatrician, be open to the idea that maybe there is anxiety,” even in a young child, Dr. Busman said. Separation anxiety can be a problem even in children who are able to go to school, she said. Parents should pay attention if a child can’t be left with a babysitter, a child can’t sleep alone at home.“These are the kids, they go into the bathroom, and they’re like, are you still there?” she said. “We do see really young anxious children.”

“If your child is suffering distress and dysfunction, reach out to your pediatrician,” Dr. Koplewicz said. When you get to a mental health professional, “make sure you ask the right questions,” he said, including asking whether that person has specific experience with treating anxiety and how long the treatment is expected to take.

“You want a professional who understands what they’re doing and can explain to you what they’re doing.”